Update dependency ranges

[whymarrh]

Context:

keythereum/package.json

Lines 28 to 35 in 4fc9842

	"dependencies": {
	"crypto-browserify": "3.12.0",
	"keccak": "1.4.0",
	"scrypt": "6.0.3",
	"secp256k1": "3.5.0",
	"sjcl": "1.0.6",
	"uuid": "3.0.0"
	},

All the dependencies listed in the package.json file are fixed to exact versions. Is there a particular reason why this is? For a library package, keythereum should allow minor and patch versions to be used (and allow npm to deduplicate them in consuming applications).